Transmission fluid change at 50k is what I would do (and what I have done during my ownership), and a coolant flush is probably a good idea as well, especially if it has never been done before. Spark plugs can wait until 100k unless something goes wrong with them.
It isn't a bad idea to get recommended maintenance done when the manufacturer calls for it, but since they recommend a 7500 mile oil change, I wouldn't bother following it (unless it's important). I have never taken my car in for the manufacturer's recommended services, and I've been just fine. Just replacing things that break/fail, as well as oil changes and tire rotations.